TORONTO (AP) — Alberta's premier says if the Obama administration rejects the Keystone XL pipeline it be would be a significant thorn in Canadian-U.S. relations.

Premier Alison Redford said in a telephone interview with The Associated Press that the issue would keep coming up. Redford is in Washington for her fourth trip to lobby on behalf of a pipeline that Canada sees as critical to its economic well-being.

Alberta has the world's third-largest reserves of oil. The proposed pipeline would carry oil from the Alberta oil sands to Texas Gulf Coast refineries.

The Obama administration is considering whether to clear the project. A decision is expected this summer.

Obama's initial rejection of the pipeline last year went over badly in Canada, which relies on the U.S. for 97 percent of its energy exports.